Air-conditioner for vehicle

ABSTRACT

An air-conditioner includes a refrigeration cycle device having an evaporator for evaporating refrigerant discharged from a compressor to cool air to be sent into a vehicle compartment. A controller turns on the compressor when a surface temperature of the evaporator or a downstream temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value. The controller turns off the compressor when a changing rate of the surface temperature or a changing rate of the downstream temperature is equal to or larger than a second predetermined value. The controller turns on the compressor again when the surface temperature or the downstream temperature becomes equal to or larger than a third predetermined value, which is larger than the first predetermined value.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-129456 filed on May 8, 2006, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioner, which is typically used in a vehicle.

2. Description of Related Art

JP-A-7-246832 discloses an air-conditioner for a vehicle. A duct sensor detects a temperature of a compressor, or a temperature of air at a downstream side of an evaporator, and the detected temperature is defined as a recognition temperature. The air-conditioner detects the lowest value among the recognition temperatures, and calculates deviation of the lowest value relative to a determination temperature for determining a start or stop of the compressor. When the calculated deviation is equal to or larger than a predetermined value, the determination temperature is increased. Thereby, freezing of the evaporator can be reduced.

After the compressor is stopped, the recognition temperature detected by the duct sensor continues to decrease to follow an actual evaporator temperature. As the actual evaporator temperature becomes lower, the lowest value of the recognition temperatures becomes lower.

However, the deviation is calculated only after the lowest value of the recognition temperatures is detected. Therefore, the freezing of the evaporator may be generated while the recognition temperature is decreasing toward the lowest value. That is, the above-described control is a feedback control, which may not be able to prevent the freezing of the evaporator.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, it is an object of the present invention to provide an air-conditioner, in which freezing of an evaporator can be reduced due to a feed-forward control.

According to a first example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent into a vehicle compartment. The controller turns on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state. The controller turns off the compressor when a changing rate of the surface temperature of the evaporator or a changing rate of the temperature of air at the downstream side of the evaporator is equal to or larger than a second predetermined value. The controller turns on the compressor again when the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator becomes equal to or larger than a third predetermined value, which is larger than the first predetermined value.

According to a second example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment. The controller turns on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state. The controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a revolution number of an engine for driving the compressor, when the controller detects that the revolution number is equal to or larger than a second predetermined value. The controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.

According to a third example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment. The controller turns on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state. The controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a temperature outside of the vehicle compartment, when the controller detects that the temperature outside of the vehicle compartment is equal to or smaller than a second predetermined value. The controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.

According to a fourth example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment. The controller turns on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state. The controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a voltage applied to a blower for sending air to the evaporator, when the controller detects that the voltage is equal to or smaller than a second predetermined value. The controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.

According to a fifth example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment. The controller turns on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state. The controller detects at least two conditions among conditions, in which a revolution number of an engine for driving the compressor is equal to or larger than a second predetermined value, a temperature outside of the vehicle compartment is equal to or smaller than a third predetermined value, and a voltage applied to a blower for sending air to the evaporator is equal to or smaller than a fourth predetermined value. The controller calculates each of the surface temperature of the evaporator and the temperature of air at the downstream side of the evaporator based on the detected conditions. The controller uses a higher temperature between the calculated surface temperature of the evaporator and the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.

According to a sixth example of the present invention, an air-conditioner for a vehicle includes a refrigeration cycle device and a controller. The refrigeration cycle device includes an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment. The controller turns on the compressor by detecting a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator. The controller detects a freezing condition predicting a freezing of the evaporator to be generated while the evaporator is cooled toward a lowest temperature state. The controller raises the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator to turn on the compressor, and continues to control the compressor, when the controller detects the freezing condition.

Accordingly, freezing of the evaporator can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic diagram showing an air-conditioner according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing the air-conditioner;

FIG. 3A, FIG. 3B and FIG. 3C are graphs showing relationships between an evaporator surface temperature and a sensor detection temperature when load of air taken into an evaporator is relatively low;

FIG. 4A, FIG. 4B and FIG. 4C are graphs showing relationships between an evaporator surface temperature and a sensor detection temperature when load of air taken into an evaporator is relatively middle;

FIG. 5A, FIG. 5B and FIG. 5C are graphs showing relationships between an evaporator surface temperature and a sensor detection temperature when load of air taken into an evaporator is relatively high;

FIG. 6 is a flow chart showing control of a compressor in the air-conditioner of the first embodiment;

FIG. 7 is a flow chart showing control of a compressor in an air-conditioner according to a second embodiment;

FIG. 8 is a flow chart showing a subroutine A in FIG. 7;

FIG. 9 is a flow chart showing control of a compressor in an air-conditioner according to a third embodiment;

FIG. 10 is a flow chart showing a subroutine B in FIG. 9;

FIG. 11 is a flow chart showing control of a compressor in an air-conditioner according to a fourth embodiment;

FIG. 12 is a flow chart showing a subroutine C in FIG. 11; and

FIG. 13 is a flow chart showing control of a compressor in an air-conditioner according to a fifth embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

As shown in FIG. 1, an air-conditioner includes an air-conditioning unit 1 and a refrigeration cycle device 10, and is typically used for a vehicle. An evaporator 9 is disposed in the air-conditioning unit 1. Refrigerant for cooling air sent into a vehicle compartment flows in the evaporator 9 and the refrigeration cycle device 10. When the air-conditioning unit 1 is disposed in an instrument panel at a front part of the vehicle, the air-conditioning unit 1 is used for conditioning air adjacent to a front seat in the vehicle compartment. When the air-conditioning unit 1 is disposed in a trunk or a side-trim at a rear part of the vehicle, the air-conditioning unit 1 is used for conditioning air adjacent to a rear seat in the vehicle compartment.

The air-conditioning unit 1 has a case 2, and the case 2 has an air passage, through which air is sent toward an occupant in the vehicle compartment. An intake air switching box 5 is disposed at an upstream part of the air passage, and includes an inside air inlet 3 for taking air inside of the vehicle compartment and an outside air inlet 4 for taking air outside of the vehicle compartment. A door 6 is rotatably disposed in the intake air switching box 5. When the door 6 closes the inside air inlet 3, air is taken into the box 5 through the outside air inlet 4. When the door 6 closes the outside air inlet 4, air is taken into the box 5 through the inside air inlet 3. The door 6 is driven by a servomotor 7. An inside air mode and an outside air mode can be switched by the servomotor 7. In the inside air mode, inside air inside of the vehicle compartment is introduced into the box 5 through the inside air inlet 3. In the outside air mode, outside air outside of the vehicle compartment is introduced into the box 5 through the outside air inlet 4.

A blower 8 is disposed at a downstream side of the box 5, and sends air toward the vehicle compartment. The blower 8 has a centrifugal air-sending fan 8 a, which is driven by a motor 8 b. The evaporator 9 is disposed at a downstream side of the blower 8, and cools air flowing in the case 2. The evaporator 9 is a heat exchanger for cooling air sent by the blower 8.

The refrigeration cycle device 10 constructs a refrigeration cycle, in which the evaporator 9, a compressor 11, a condenser 12, a receiver 13 and a thermal expansion valve 14 (decompressor) are connected in a loop. Refrigerant circulates from a discharge side of the compressor 11 into the evaporator 9 through the condenser 12, the receiver 13 and the thermal expansion valve 14.

The compressor 11 compresses refrigerant to have a high-temperature and high-pressure. The high-pressure gas refrigerant is discharged from the compressor 11, and introduced into the condenser 12. The gas refrigerant exchanges heat with outside air sent and cooled by an electrical fan 12 a. Therefore, heat is emitted from the gas refrigerant, and the gas refrigerant is condensed in the condenser 12. Refrigerant passing through the condenser 12 is separated into a liquid-phase refrigerant and a gas-phase refrigerant in the receiver 13, and the liquid-phase refrigerant is stored in the receiver 13.

High-pressure liquid-phase refrigerant discharged from the receiver 13 is decompressed by the thermal expansion valve 14 into a gas-liquid two-phase state. The decompressed low-pressure refrigerant is evaporated in the evaporator 9, because the decompressed low-pressure refrigerant absorbs heat from air. Gas refrigerant evaporated by the evaporator 9 is again taken into the compressor 11, and compressed by the compressor 11.

An open degree of the valve 14 is automatically controlled such that refrigerant at an outlet of the evaporator 9 has a predetermined superheat degree. The compressor 11, the condenser 12 and the receiver 13 of the refrigeration cycle device 10 are arranged in an engine compartment (not shown) of the vehicle.

A heater core 15 is arranged at a downstream side of the evaporator 9 in the air-conditioning unit 1, and heats air flowing through the case 2. The heater core 15 is a heat exchanger for heating air passing through the evaporator 9 by using coolant of a vehicle engine (not shown) as a heat source. A bypass passage 16 is arranged adjacent to the heater core 15, and air bypassing the heater core 15 flows in the bypass passage 16.

An air-mixing door 17 is rotatably arranged between the evaporator 9 and the heater core 15. The air-mixing door 17 is driven by a servomotor 18, and a rotational position and an open degree of the air-mixing door 17 can be continuously controlled. An amount of warm air passing through the heater core 15 and an amount of cool air passing through the bypass passage 16 can be controlled by the open degree of the air-mixing door 17. Thus, a temperature of air blown into the vehicle compartment can be controlled.

A defrost air outlet 19, a face air outlet 20 and a foot air outlet 21 are arranged at a downstream side of the air passage of the case 2. Air-conditioning air is blown toward a window of the vehicle through the defrost air outlet 19. Air-conditioning air is blown toward an upper body of an occupant through the face air outlet 20. Air-conditioning air is blown toward foot of an occupant through the foot air outlet 21.

A defrost air door 22 is rotatably arranged at an upstream side of the defrost air outlet 19. A face air door 23 is rotatably arranged at an upstream side of the face air outlet 20. A foot air door 24 is rotatably arranged at an upstream side of the foot air outlet 21. Each of the doors 22, 23, 24 is opened or closed by a single servomotor 25 through a link mechanism (not shown).

The compressor 11 is driven when a rotation power is transmitted from the vehicle engine to the compressor 11 through a pulley 11 a and a belt (not shown). An amount of refrigerant discharged from the compressor 11 can be continuously controlled in response to a control signal output from outside, because a capacity-variable compressor is used as the compressor 11. The compressor 11 includes a control valve 110 for controlling its capacity. Specifically, the compressor 11 has a swash plate, and a pressure in a swash plate room is controlled by using refrigerant discharge pressure and refrigerant suck pressure. Thereby, piston stroke can be controlled by a gradient angle of the swash plate. Thus, capacity for discharging refrigerant from the compressor 11 can be continuously controlled in a range approximately between 0% and 100%.

Next, an air-conditioning electric control unit (ECU) 28 will be described with reference to FIG. 2. The ECU 28 is an electrical controller of the air-conditioner, and includes a known microcomputer having a CPU, ROM and RAM, and peripheral circuitry. The ROM has a control program for controlling air-conditioning operation, and the ECU 28 performs a variety of calculations and treatments.

Sensor detection signals output from sensors 26, and operation signals output from an air-conditioning panel 27 are input into an input side of the ECU 28. The sensors 26 are constructed with an evaporator temperature sensor 26 a, an outside air temperature sensor 26 b, an inside air temperature sensor 26 c, a solar radiation sensor 26 d and a coolant temperature sensor 26 e. The evaporator temperature sensor 26 a detects an evaporator surface temperature Te of the evaporator 9. The outside air temperature sensor 26 b detects an outside air temperature Tam. The inside air temperature sensor 26 c detects an inside air temperature Tr. The solar radiation sensor 26 d detects a solar radiation amount Ts. The coolant temperature sensor 26 e detects a coolant temperature Tw. Further, an evaporator downstream temperature sensor (not shown) is disposed at an air-emitting part of the evaporator 9, and detects a temperature of air at a downstream side of the evaporator 9. A sensor signal output from this evaporator downstream temperature sensor is also input into the ECU 28.

The air-conditioning panel 27 is arranged adjacent to an instrument panel (not shown) in front of a driver seat in the vehicle compartment. Switches 27 a, 27 b, 27 c, 27 d and 27 e are provided in the air-conditioning panel 27, and operated by an occupant, e.g., driver. A target temperature of the vehicle compartment is set through the temperature switch 27 a, and the temperature switch 27 a outputs a signal of the target temperature into the ECU 28. An inlet mode by the door 6 (the inside air inlet 3 or the outside air inlet 4) is switched by the inlet switch 27 b, and the inlet switch 27 b outputs a signal for changing the inlet mode into the ECU 28. An air-blowing mode is switched by the air-blowing mode switch 27 c, and the air-blowing mode switch 27 c outputs a signal for setting a face mode, bi-level mode, foot mode, foot defrost mode or defrost mode as the air-blowing mode. An amount of air sent by the blower 8 is controlled through the air amount switch 27 d, and the air amount switch 27 d outputs a signal for setting the amount of air sent by the blower 8. Further, the blower 8 is turned on or off through the air amount switch 27 d. The air-conditioning switch 27 e is used for turning on or off the compressor 11. When the air-conditioning switch 27 e is turned off, a control current In supplied to the control valve 110 of the compressor 11 is forcibly made zero. Thus, the discharge capacity of the compressor 11 is made approximately zero, and the compressor 11 is in a stop state. When the air-conditioning switch 27 e is turned on, the control current In having a predetermined value calculated by the ECU 28 is output into the control valve 110 of the compressor 11.

The control valve 110 of the compressor 11 controls the discharge capacity of the compressor 11, and has an electromagnetic coil 112 a. The electromagnetic coil 112 a, the servomotors 7, 18, 25 and the motor 8 b are connected to an output side of the ECU 28, and controlled by output signals output from the ECU 28.

Next, operation of the air-conditioner will be described. When the air amount switch 27 d of the air-conditioning panel 27 is turned on, the blower 8 starts to operate and sends air in the air-conditioning unit 1. Then, when the air-conditioning switch 27 e is turned on, the control current In having the predetermined value calculated by the ECU 28 is output into the control valve 110 of the compressor 11. The vehicle engine drives the compressor 11 to have a predetermined discharge capacity. That is, the compressor 11 is in an operation state.

Thereby, refrigerant circulates in the evaporator 9 of the refrigeration cycle device 10, and air in the air-conditioning unit 1 is cooled and dehumidified by the evaporator 9. Thus, air-conditioning air can be emitted into the vehicle compartment.

The ECU 28 controls the discharge capacity of the compressor 11. After detection signals output from the sensors 26, and operation signals input into the air-conditioning panel 27 are input into the ECU 28, the ECU 28 calculates a target temperature TAO of air blown into the vehicle compartment. An occupant sets a target temperature Tset of the vehicle compartment through the temperature switch 27 a of the air-conditioning panel 27. The target temperature TAO is a temperature of air blown into the vehicle compartment in order to keep the vehicle compartment to have the target temperature Tset, even if heat load fluctuates. The target temperature TAO of air blown into the vehicle compartment is calculated based on the target temperature Tset of the vehicle compartment, the outside air temperature Tam, the inside air temperature Tr, and the solar radiation amount Ts.

Further, the ECU 28 calculates a target temperature of air blown from the evaporator 9, and calculates the control current In to control the capacity of the compressor 11. An actual temperature of air at a downstream side of the evaporator 9 is detected by the above-described evaporator downstream temperature sensor for detecting the temperature of air at the downstream side of the evaporator 9. The control current In is basically determined such that the actual temperature of air at the downstream side of the evaporator 9 becomes approximately equal to the target temperature of air blown from the evaporator 9. Then, the control current In is output into the coil 112 a of the valve 110, and the capacity of the compressor 11 starts to be controlled.

Next, a relationship between an evaporator surface temperature and a sensor detection temperature of the evaporator surface temperature, which is detected by the sensor 26 a, will be described with reference to FIGS. 3A-5C, when the compressor 11 is turned on or off. In FIGS. 3A-5C, nine conditions are selected from various operation conditions, and a response delay of the sensor detection temperature relative to the evaporator surface temperature, temperature changing rates of the sensor detection temperature and the evaporator surface temperature, and a temperature difference between the sensor detection temperature and the evaporator surface temperature are shown.

The sensor detection temperature is an evaporator surface temperature detected by the evaporator temperature sensor 26 a. Data of the evaporator surface temperature are sampled at least three or four times, and the temperature changing rate of the evaporator surface temperature is calculated by averaging the data. The temperature changing rate represents a temperature variation per unit time. That is, the temperature changing rate is a gradient of a graph of the temperature. A double-chained line in FIGS. 3A-5C represents a timing for turning on or off the compressor 11. A dashed line in FIGS. 3A-5C represents the evaporator surface temperature, and a solid line in FIGS. 3A-5C represents the sensor detection temperature. Freezing of the evaporator 9 is generated in an area A, B and C of FIGS. 3A-5C.

In FIGS. 3A-3C, load of air taken into the evaporator 9 is relatively low, and a voltage applied to the blower 8 is different. As shown in FIG. 3A, the sensor detection temperature has the changing rate of 0.6° C./sec, and the evaporator surface temperature and the sensor detection temperature have a temperature difference of 3.0° C. at the maximum. As shown in FIG. 3B, the sensor detection temperature has the changing rate of 0.6° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 4.0° C. at the maximum. As shown in FIG. 3C, the sensor detection temperature has the changing rate of 0.6° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 4.8° C. at the maximum.

In FIGS. 4A-4C, load of air taken into the evaporator 9 is relatively middle, and a voltage applied to the blower 8 is different. As shown in FIG. 4A, the sensor detection temperature has the changing rate of 0.7° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 3.7° C. at the maximum. As shown in FIG. 4B, the sensor detection temperature has the changing rate of 0.8° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 5.1° C. at the maximum. As shown in FIG. 4C, the sensor detection temperature has the changing rate of 0.8° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 5.2° C. at the maximum.

In FIGS. 5A-5C, air taken into the evaporator has a relatively high load, and a voltage applied to the blower 8 is different. As shown in FIG. 5A, the sensor detection temperature has the changing rate of 0.4° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 1.5° C. at the maximum. As shown in FIG. 5B, the sensor detection temperature has the changing rate of 0.7° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 3.5° C. at the maximum. As shown in FIG. 5C, the sensor detection temperature has the changing rate of 0.7° C./sec, and the evaporator surface temperature and the sensor detection temperature have the temperature difference of 4.2° C. at the maximum.

Due to the response delay, the sensor detection temperature becomes higher than the evaporator surface temperature by about 5° C. at the maximum. Further, if the evaporator surface temperature is equal to or larger than −2° C., the freezing of the evaporator 9 is not generated while the compressor 11 is controlled on and off. Therefore, if the compressor 11 is turned off when the sensor detection temperature is equal to or larger than 3° C. (5° C.-2° C.), the freezing of the evaporator 9 can be reduced, while the freezing of the evaporator 9 is easily generated when the evaporator 9 has a high cooling speed.

Further, based on the nine conditions shown in FIGS. 3A-5C, when the changing rate of the sensor detection temperature is equal to or larger than 0.5° C./sec, the freezing of the evaporator 9 is generated in the area A, B, C. Therefore, a marginal (limit) speed for the freezing of the evaporator 9 is defined as 0.5° C./sec. Furthermore, the evaporator surface temperature is further decreased while the changing rate of the evaporator surface temperature is measured. Therefore, a temperature for turning off the compressor 11 is set to have allowance of about 1° C./sec. Thus, determination for turning off the compressor 11 is to be performed when the sensor detection temperature is smaller than 4° C. (3° C.+1° C.).

Next, control of the compressor 11 to reduce the freezing of the evaporator 9 in advance will be described with reference to FIG. 6. When the air-conditioning switch 27 e is turned on, the ECU 28 determines that a sensor detection temperature TE detected by the evaporator temperature sensor 26 a is smaller than a first predetermined temperature R1 (e.g., 4° C.) or not (S100). The ECU 28 repeats S100 until the ECU 28 determines that the sensor detection temperature TE is smaller than the first predetermined temperature R1. After the ECU 28 determines that the sensor detection temperature TE is smaller than the first predetermined temperature R1, the ECU 28 determines that the changing rate of the sensor detection temperature TE is equal to or larger than a second predetermined value R2 or not (S110). Here, as an example, the ECU 28 determines that a temperature change between adjacent sampling timings is equal to or larger than 0.6° C./sec or not (TE(n−1)−TE(n)≧0.6).

When the ECU 28 determines that the changing rate of the sensor detection temperature TE is smaller than the second predetermined value R2 at S110, the ECU 28 determines that the freezing of the evaporator 9 is not generated, and performs default (ordinary) control of the compressor 11 (S170). The default control is performed based on a control characteristic map shown of S170 in FIG. 6. The sensor detection temperature TE is applied in the map as a temperature TEO. When the compressor 11 is operating, the compressor 11 is turned off at the temperature TEO. When the compressor 11 is not operating, the compressor 11 is turned on at a predetermined temperature (TEO+1° C.), which is 1° C. higher than the temperature TEO. The control characteristic map is stored in the ECU 28 in advance.

Here, the sensor detection temperature TE is smaller than 4° C., so that the compressor 11 is turned on when the sensor detection temperature TE is smaller than 5° C. (4° C.+1° C.). Thus, when the ECU 28 detects that the sensor detection temperature TE is equal to or larger than the predetermined temperature (TEO+1° C.), the ECU 28 performs the default control to turn on the compressor 11, in accordance with the map of S170.

When the ECU 28 determines that the changing rate of the sensor detection temperature TE is equal to or larger than the second predetermined value (0.6° C./sec) at S110, the ECU 28 turns off the compressor 11 (S120). This is because the cooling speed of the evaporator 9 is so fast that the freezing of the evaporator 9 may be generated. That is, the ECU 28 determines that the freezing of the evaporator 9 will be generated. Thereby, a flow of refrigerant is stopped in the refrigeration cycle device 10, so that the evaporator surface temperature will be increased. Then, the ECU 28 determines that the sensor detection temperature TE is equal to or larger than a third predetermined temperature R3 (e.g., 5° C.) or not (S130). The third predetermined temperature R3 is higher than the predetermined temperature (TEO+1° C.).

The ECU 28 repeats S130 and keeps the compressor 11 off, until when the ECU 28 determines that the sensor detection temperature TE is equal to or larger than the third predetermined temperature R3. When the ECU 28 determines that the sensor detection temperature TE is equal to or larger than the third predetermined temperature R3, the ECU 28 turns on the compressor 11 (S140). This is because the freezing of the evaporator 9 can be avoided, and the ECU 28 determines that the temperature of the evaporator 9 is increased, so that the evaporator 9 is needed to be cooled. Thus, the ECU 28 continuously performs S100-S170 while the air-conditioner is operating.

The sensor detection temperature is either the evaporator surface temperature detected by the evaporator temperature sensor 26 a, or the temperature of air at the downstream side of the evaporator 9, which is detected by the evaporator downstream temperature sensor (not shown). In either case, the sensor detection temperature has the above-described response delay relative to the evaporator surface temperature, which is actually fluctuating. The ECU 28 controls the compressor 11 in consideration of the response delay.

According to the first embodiment, in a case where the compressor 11 is in stop state, when the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 is equal to or larger than the predetermined temperature (TEO+1° C.), the ECU 28 turns on the compressor 11. When the changing rate of the evaporator surface temperature or the changing rate of the temperature of air at the downstream side of the evaporator 9 is equal to or larger than the second predetermined value (0.6° C./sec), the ECU 28 turns off the compressor 11. Then, when the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 becomes equal to or larger than the third predetermined temperature R3 (5° C.), which is larger than the predetermined temperature (TEO+1° C.), the ECU 28 turns on (restarts) the compressor 11.

Thus, possibility of the freezing of the evaporator 9 can be predictable in advance, while the evaporator 9 is cooled and the temperature of the evaporator 9 is decreased. Therefore, this feed-forward control can effectively reduce the freezing of the evaporator 9.

Further, by increasing the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 to turn on the compressor 11, control capable of reducing the freezing of the evaporator 9 can be provided. Therefore, a temperature of air blown into the vehicle compartment can be restricted from increasing, and odorous component can be restricted from flowing into the vehicle compartment. Thus, air blown into the vehicle compartment can provide better feeling to an occupant, and operation time of the refrigeration cycle device 10 can be reduced so that power saving effect can be enhanced.

Second Embodiment

A control of the compressor 11 in a second embodiment will be described with reference to FIGS. 7 and 8. When the air-conditioning switch 27 e is turned on, the ECU 28 performs a subroutine A shown in FIG. 8 (S150 in FIG. 7).

As shown in FIG. 8, in the subroutine A, the ECU 28 performs a treatment for detecting a revolution number Ne(rpm) of the vehicle engine (S151). Next, when the detected revolution number Ne is equal to or larger than a predetermined value N1, the ECU 28 applies the detected revolution number Ne into a control characteristic map of S152, and calculates an evaporator surface temperature TEOA. The predetermined value N1 is a revolution number capable of causing the freezing of the evaporator 9, because the compressor 11 has a high capacity for compressing refrigerant. The predetermined value N1 is determined based on experiments, and memorized in the ECU 28 in advance.

When the detected revolution number Ne is between N1 and N2, the evaporator surface temperature TEOA is interpolated between 1° C. and 4° C. When the detected revolution number Ne is equal to or larger than N2, the evaporator surface temperature TEOA is constant (4° C.). The control characteristic map is stored in the ECU 28 in advance.

The treatment for detecting that the revolution number Ne is equal to or larger than the predetermined value N1 is performed at least while the evaporator 9 is cooled toward the lowest temperature state. Thereafter, the treatment detects and predicts a condition for generating the freezing of the evaporator 9. When the condition for generating the freezing of the evaporator 9 is detected, the evaporator surface temperature TEOA is calculated based on the control characteristic map of S152. Thereby, a reference evaporator surface temperature for turning on the compressor 11 is further increased.

Next, the ECU 28 applies the evaporator surface temperature TEOA calculated in the subroutine A into the temperature TEO of a control characteristic map of S153 in FIG. 7. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to the evaporator surface temperature TEOA, the compressor 11 is turned off. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to a temperature 1° C. higher than the evaporator surface temperature TEOA, the compressor 11 is turned on. Thus, the compressor 11 is continuously controlled. The ECU 28 repeats this series of the feed-forward control to prevent the freezing of the evaporator 9 while the air-conditioning switch 27 e is on.

The evaporator surface temperature detected by the evaporator temperature sensor 26 a is used as the reference evaporator surface temperature for turning on the compressor 11. Alternatively, a temperature of air at the downstream side of the evaporator 9 may be used as the reference evaporator surface temperature. In this case, the temperature of air at the downstream side of the evaporator 9 is processed by the subroutine A, and the reference evaporator surface temperature is determined, similarly to the evaporator surface temperature.

According to the second embodiment, while the evaporator 9 is cooled toward the lowest temperature state, the ECU 28 detects the condition predicting the freezing of the evaporator 9. When the condition is detected, the reference evaporator surface temperature or the reference temperature of air at the downstream side of the evaporator 9 for turning on the compressor 11 is increased, so that the compressor 11 is continuously controlled.

Thus, the ECU 28 can perform the feed-forward control to prevent the freezing of the evaporator 9 in advance. By increasing the temperature of air at the downstream side of the evaporator 9 to turn on the compressor 11, air blown into the vehicle compartment can provide better feeling to the occupant, and operation time of the refrigeration cycle device 10 can be reduced so that power saving effect can be enhanced.

Further, when the ECU 28 detects that the revolution number Ne of the engine is equal to or larger than the predetermined value N1, the ECU 28 calculates to increase the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 based on the detected revolution number. The calculated evaporator surface temperature or the calculated temperature of air at the downstream side of the evaporator 9 is used for turning on the compressor 11. When the revolution number Ne of the engine is equal to or larger than predetermined value N1, the compressor 11 has a high capacity for compressing refrigerant, and the freezing of the evaporator 9 can be easily generated.

Thus, the freezing of the evaporator 9 can be predictable by detecting that the revolution number Ne of the engine is equal to or larger than the predetermined value N1, because the compressor 11 has the high capacity for compressing refrigerant. Further, the freezing of the evaporator 9 can be effectively reduced, because the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 calculated based on the capacity for compressing refrigerant is used for turning on the compressor 11.

Other parts in the second embodiment will be made similar to the first embodiment.

Third Embodiment

A control of the compressor 11 in a third embodiment will be described with reference to FIGS. 9 and 10. When the air-conditioning switch 27 e is turned on, the ECU 28 performs a subroutine B shown in FIG. 10 (S154 in FIG. 9).

As shown in FIG. 10, in the subroutine B, the ECU 28 performs a treatment for detecting an outside air temperature TAM(° C.) through the outside air temperature sensor 26 b (S155). Next, when the detected outside air temperature TAM is equal to or smaller than a predetermined value T2, the ECU 28 applies the detected outside air temperature TAM into a control characteristic map of S156, and calculates an evaporator surface temperature TEOB. The predetermined value T2 is an outside air temperature capable of causing the freezing of the evaporator 9, because the condenser 12 has a high cooling capacity. The predetermined value T2 is determined based on experiments, and memorized in the ECU 28 in advance.

When the detected outside air temperature TAM is between T1 and T2, the evaporator surface temperature TEOB is interpolated between 1° C. and 4° C. When the detected outside air temperature TAM is equal to or smaller than T1, the evaporator surface temperature TEOB is constant (4° C.). The control characteristic map is stored in the ECU 28 in advance.

The treatment for detecting that the outside air temperature TAM is equal to or smaller than the predetermined value T2 is performed at least while the evaporator 9 is cooled toward the lowest temperature state. Thereafter, the treatment detects and predicts a condition for generating the freezing of the evaporator 9. When the condition for generating the freezing of the evaporator 9 is detected, the evaporator surface temperature TEOB is calculated based on the control characteristic map of S156. Thereby, a reference evaporator surface temperature for turning on the compressor 11 is further increased.

Next, the ECU 28 applies the evaporator surface temperature TEOB calculated in the subroutine B into the temperature TEO of a control characteristic map of S157 in FIG. 9. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to the evaporator surface temperature TEOB, the compressor 11 is turned off. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to a temperature 1° C. higher than the evaporator surface temperature TEOB, the compressor 11 is turned on. Thus, the compressor 11 is continuously controlled. The ECU 28 repeats this series of the feed-forward control to prevent the freezing of the evaporator 9 while the air-conditioning switch 27 e is on.

The evaporator surface temperature detected by the evaporator temperature sensor 26 a is used as the reference evaporator surface temperature for turning on the compressor 11. Alternatively, a temperature of air at the downstream side of the evaporator 9 may be used as the reference evaporator surface temperature. In this case, the temperature of air at the downstream side of the evaporator 9 is processed by the subroutine B, and the reference evaporator surface temperature is determined, similarly to the evaporator surface temperature.

According to the third embodiment, when the ECU 28 detects that outside air temperature TAM outside of the vehicle compartment is equal to or smaller than the predetermined value N2, the ECU 28 calculates to increase the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 based on the detected outside air temperature. The calculated evaporator surface temperature or the calculated temperature of air at the downstream side of the evaporator 9 is used for turning on the compressor 11. When the outside air temperature TAM is equal to or smaller than predetermined value T2, the condenser 12 has a high cooling capacity, and the freezing of the evaporator 9 can be easily generated.

Thus, the freezing of the evaporator 9 can be predictable by detecting that the outside air temperature TAM is equal to or smaller than the predetermined value T2, because the condenser 12 has the high cooling capacity. Further, the freezing of the evaporator 9 can be effectively reduced, because the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 calculated based on the outside air temperature TAM is used for turning on the compressor 11.

Other parts in the third embodiment will be made similar to the first embodiment.

Fourth Embodiment

A control of the compressor 11 in a fourth embodiment will be described with reference to FIGS. 11 and 12. When the air-conditioning switch 27 e is turned on, the ECU 28 performs a subroutine C shown in FIG. 12 (S158 in FIG. 11).

As shown in FIG. 12, in the subroutine C, the ECU 28 performs a treatment for detecting a voltage Vb(V) applied to the blower 8 for sending air toward the evaporator 9 (S159). Next, when the detected voltage Vb is equal to or smaller than a predetermined value V2, the ECU 28 applies the detected voltage Vb into a control characteristic map of S160, and calculates an evaporator surface temperature TEOC. The predetermined value V2 is a voltage capable of causing the freezing of the evaporator 9, because the evaporator 9 has a high cooling speed. The predetermined value V2 is determined based on experiments, and memorized in the ECU 28 in advance.

When the detected voltage Vb is between V1 and V2, the evaporator surface temperature TEOC is interpolated between 1° C. and 4° C. When the detected voltage Vb is equal to or smaller than V1, the evaporator surface temperature TEOC is constant (4° C.). The control characteristic map is stored in the ECU 28 in advance.

The treatment for detecting that the voltage Vb is equal to or smaller than the predetermined value V2 is performed at least while the evaporator 9 is cooled toward the lowest temperature state. Thereafter, the treatment detects and predicts a condition for generating the freezing of the evaporator 9. When the condition for generating the freezing of the evaporator 9 is detected, the evaporator surface temperature TEOC is calculated based on the control characteristic map of S160. Thereby, a reference evaporator surface temperature for turning on the compressor 11 is further increased.

Next, the ECU 28 applies the evaporator surface temperature TEOC calculated in the subroutine C into the temperature TEO of a control characteristic map of S161 in FIG. 11. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to the evaporator surface temperature TEOC, the compressor 11 is turned off. When the evaporator surface temperature detected by the evaporator temperature sensor 26 a is equal to a temperature 1° C. higher than the evaporator surface temperature TEOC, the compressor 11 is turned on. Thus, the compressor 11 is continuously controlled. The ECU 28 repeats this series of the feed-forward control to prevent the freezing of the evaporator 9 while the air-conditioning switch 27 e is on.

The evaporator surface temperature detected by the evaporator temperature sensor 26 a is used as the reference evaporator surface temperature for turning on the compressor 11. Alternatively, a temperature of air at the downstream side of the evaporator 9 may be used as the reference evaporator surface temperature. In this case, the temperature of air at the downstream side of the evaporator 9 is processed by the subroutine C, and the reference evaporator surface temperature is determined, similarly to the evaporator surface temperature.

According to the fourth embodiment, when the ECU 28 detects that the voltage Vb applied to the blower 8 is equal to or smaller than the predetermined value V2, the ECU 28 calculates to increase the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 based on the detected voltage. The calculated evaporator surface temperature or the calculated temperature of air at the downstream side of the evaporator 9 is used for turning on the compressor 11. When the detected voltage is equal to or smaller than predetermined value V2, the evaporator 9 has a high cooling speed, and the freezing of the evaporator 9 can be easily generated.

Thus, the freezing of the evaporator 9 can be predictable by detecting that the voltage Vb applied to the blower 8 is equal to or smaller than the predetermined value V2, because the evaporator 9 has the high cooling speed. Further, the freezing of the evaporator 9 can be effectively reduced, because the evaporator surface temperature or the temperature of air at the downstream side of the evaporator 9 calculated based on the voltage Vb applied to the blower 8 is used for turning on the compressor 11.

Other parts in the fourth embodiment will be made similar to the first embodiment.

Fifth Embodiment

A control of the compressor 11 in a fifth embodiment will be described with reference to FIGS. 13, 8, 10 and 12. As shown in FIG. 13, the subroutine A of the second embodiment, the subroutine B of the third embodiment and the subroutine C of the fourth embodiment are performed in the fifth embodiment. Thereafter, a maximum temperature among the evaporator surface temperatures calculated in the subroutines A, B, C is determined at S162, and the maximum temperature is used in S163.

The subroutines A, B, C may be processed in any order. For example, the subroutines A, B, C may be processed parallel to each other. Further, only any two of the subroutines A, B, C may be performed.

The subroutine A detects a condition, in which the revolution number Ne of the vehicle engine is equal to or larger than the predetermined value N1. The subroutine B detects a condition, in which the outside air temperature TAM is equal to or smaller than T2. The subroutine C detects a condition, in which the voltage Vb applied to the blower 8 for sending air to the evaporator 9 is equal to or smaller than the predetermined value V2. When the ECU 28 detects at least one of the conditions, the freezing of the evaporator 9 is determined to be easily generated.

In this case, the conditions are monitored. When at least one of the conditions is detected, the compressor 11 is turned on at the increased evaporator surface temperature or the increased temperature of air at the downstream side of the evaporator 9. Therefore, accuracy for reducing the freezing of the evaporator 9 due to the feed-forward control can be enhanced.

Further, when the ECU 28 detects at least two of the conditions, the ECU 28 calculates each of the evaporator surface temperature and the temperature of air at the downstream side of the evaporator 9 based on the detected conditions. A higher temperature between the calculated evaporator surface temperature and the calculated temperature of air at the downstream side of the evaporator 9 can be used for turning on the compressor 11.

In this case, because the compressor 11 can be turned on at the higher temperature, the freezing of the evaporator 9 can be more effectively prevented in advance. Further, operation time of the refrigeration cycle device 10 can be reduced so that power saving effect can be more enhanced.

Further, when the ECU 28 detects at least two of the conditions, the ECU 28 calculates to increase each of the evaporator surface temperature and the temperature of air at the downstream side of the evaporator 9 based on the detected conditions. The higher temperature between the calculated evaporator surface temperature and the calculated temperature of air at the downstream side of the evaporator 9 can be used for turning on the compressor 11.

Thus, the plural conditions, in which the freezing of the evaporator 9 can be easily generated, can be detected. By using the calculated higher temperature to control the compressor 11, the freezing of the evaporator 9 can be more effectively prevented.

Other parts in the fifth embodiment will be made similar to the first embodiment.

Other Embodiments

The capacity-variable compressor is used as the compressor 11 in the above embodiments. Alternatively, a capacity-fixed compressor may be used as the compressor 11.

Further, when the revolution number Ne of the vehicle engine is not used as a parameter to detect a condition for causing the freezing of the evaporator 9, an electric compressor using battery power may be used as the compressor 11.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

1. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent into a vehicle compartment; and a controller for turning on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state, wherein the controller turns off the compressor when a changing rate of the surface temperature of the evaporator or a changing rate of the temperature of air at the downstream side of the evaporator is equal to or larger than a second predetermined value, and the controller turns on the compressor again when the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator becomes equal to or larger than a third predetermined value, which is larger than the first predetermined value.
 2. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment; and a controller for turning on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state, wherein the controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a revolution number of an engine for driving the compressor, when the controller detects that the revolution number is equal to or larger than a second predetermined value, and the controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.
 3. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment; and a controller for turning on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state, wherein the controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a temperature outside of the vehicle compartment, when the controller detects that the temperature outside of the vehicle compartment is equal to or smaller than a second predetermined value, and the controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.
 4. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment; and a controller for turning on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state, wherein the controller calculates the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator based on a voltage applied to a blower for sending air to the evaporator, when the controller detects that the voltage is equal to or smaller than a second predetermined value, and the controller uses the calculated surface temperature of the evaporator or the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.
 5. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment; and a controller for turning on the compressor when a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator is equal to or larger than a first predetermined value while the compressor is in a stop state, wherein the controller detects at least two conditions among conditions, in which a revolution number of an engine for driving the compressor is equal to or larger than a second predetermined value, a temperature outside of the vehicle compartment is equal to or smaller than a third predetermined value, and a voltage applied to a blower for sending air to the evaporator is equal to or smaller than a fourth predetermined value, the controller calculates each of the surface temperature of the evaporator and the temperature of air at the downstream side of the evaporator based on the detected conditions, and the controller uses a higher temperature between the calculated surface temperature of the evaporator and the calculated temperature of air at the downstream side of the evaporator to turn on the compressor.
 6. An air-conditioner for a vehicle, the air-conditioner comprising: a refrigeration cycle device including an evaporator for evaporating refrigerant discharged from a compressor so as to cool air to be sent to a vehicle compartment; and a controller for turning on the compressor by detecting a surface temperature of the evaporator or a temperature of air at a downstream side of the evaporator, wherein the controller detects a freezing condition predicting a freezing of the evaporator to be generated while the evaporator is cooled toward a lowest temperature state, and the controller raises the surface temperature of the evaporator or the temperature of air at the downstream side of the evaporator to turn on the compressor, and continues to control the compressor, when the controller detects the freezing condition.
 7. The air-conditioner according to claim 6, wherein the freezing condition defines that a revolution number of an engine for driving the compressor is equal to or larger than a predetermined value.
 8. The air-conditioner according to claim 6, wherein the freezing condition defines that an outside air temperature is equal to or smaller than a predetermined value.
 9. The air-conditioner according to claim 6, wherein the freezing condition defines that a voltage applied to a blower for sending air to the evaporator is equal to or smaller than a predetermined value.
 10. The air-conditioner according to claim 6, wherein the controller is determined to detect the freezing condition, when the controller detects at least one condition among conditions, in which a revolution number of an engine for driving the compressor is equal to or larger than a first predetermined value, an outside air temperature is equal to or smaller than a second predetermined value, and a voltage applied to a blower for sending air to the evaporator is equal to or smaller than a third predetermined value.
 11. The air-conditioner according to claim 6, wherein the controller detects at least two conditions among conditions, in which a revolution number of an engine for driving the compressor is equal to or larger than a first predetermined value, an outside air temperature is equal to or smaller than a second predetermined value, and a voltage applied to a blower for sending air to the evaporator is equal to or smaller than a third predetermined value, the controller calculates each of the surface temperature of the evaporator and the temperature of air at the downstream side of the evaporator based on the detected conditions, and the controller uses a higher temperature between the calculated surface temperature of the evaporator and the calculated temperature of air at the downstream side of the evaporator to turn on the compressor. 